A light guide is a device designed to transport light from a light source to a destination area with minimal loss, and homogenously distribute the carried light in the destination area. Light is transmitted through the light guide by means of total internal reflection. Light guides are usually made of optical grade materials such as acrylic resin, polycarbonate, epoxies, and glass. Light guides are applicable in different fields of applications like medical equipment's, communication equipment's, industrial control equipment's, small space access lightings, etc. Useful in numerous applications, light guides may be used to carry lights from LED lamps on PCBs to front panels to be used for status indications, light guides may be used to collect and direct lights to backlight Liquid Crystal Display (LCD) panels or legends, and light guides may also be used as a means to illuminate grid patterns on a see through window, and so on.
Light guides may include customized shapes and a variety of lens caps. Light guides are compatible for use with either surface-mount or through-hole luminaires. Light guides are also capable of being either panel mounted or PCB mounted. Light guides may include various body types, such as flexible body types or rigid body types. The rigid body type light guides are often produced with hard plastic materials and may include either a vertical construction or a right-angle construction. The rigid body type light guides are capable of redirecting luminaire light generated outputs to a desired location with minimal loss of intensity. The rigid body type light guides may be ideal if luminaires are mounted on a PCB positioned immediately behind a front panel. On the other hand, flexible light guides are constructed with optical grade plastic materials that provide less rigidity, which allows them to transport light from a board at custom, user-specified, subtle angles ensuring easy integration around existing components. Both rigid and flexible light guides can come in single or multi-unit configurations.
Light guides may be manufactured in different shapes and sizes, such as, for example, cylindrical (wherein the cross-section is oval), rectangular (wherein the cross-section is square), and conical (wherein the cross-section increases in size from the entrance end to exit end). They may also include specialized/irregular shapes, such as, an arrow, a star, a quarter moon, etc. To achieve illumination in corners of light guides with rectangular or specialized shapes, the corners often include a radius greater than 0.5 mm (0.020 in.) and the corners are not sharp. The light guide shape may gradually change along its length. For example, the light guide may include a substantially circular shape at the entrance end (to accommodate the luminaire) and include a square shape at its exit end. The design of a light guide typically depends on three crucial factors: a) effective flux coupling to get the light from a luminaire into the light guide with minimal loss; b) transmitting the light through the light guide towards the exit surface; and, c) allowing the light to escape through the exit surface with minimal loss.
The inner surface finish of a light guide is very important to ensure proper operation. The sides parallel to the direction of light travel must be designed correctly to affect the total internal reflection and refraction. The entrance portion of the light guide must be smooth, and contoured to match the luminaire in order to allow light rays to enter with minimal reflection and then scatter, while the exit portion of the light guide must be diffused. A diffused exit may include random critical angles across its surface that provides a high probability that light rays can escape and may further help to scatter the light rays, thus producing a wide radiation pattern. For effective flux coupling and light capture, the entrance end of the light guide must be smooth and flat or concave contoured to match the light output radiation pattern and package configuration of the mating luminaire.
Existing light guide designs are specific to luminaires' shapes and designs, which may limit their use with LED based luminaires in general. LED based luminaire designs and shapes are easy to modify and manufacture, which leads to rapid field upgrades, with new designs coming out daily.
In view of the disadvantages associated with currently available currently available light guide devices and methods, there is a need for a system and a method to provide a light guide to carry light rays from a luminaire to a Printed Circuit Board (PCB), in such a manner that does not limit the distance between the luminaire and the PCB. Additionally, there is a need for a light guide that is adapted to be coupled to/affixed on various luminaires, such that the light guide performs a plurality of operations/functions on a light that exits the luminaire in favor of the light sensors. The PCB is attachable anywhere in an environment where the luminaires are located via a sensor clip (prior art). The PCB includes multiple sensors. Some of the sensors are light sensors while others face the environment (environment sensors). The plurality of operations performed by the light guide on the light supports the light sensors and the longevity and usability of the system.